Sensitivity Analysis of the Battery System State of Power

In battery-powered applications, it is necessary to estimate the battery system’s maximum allowed current/power for a certain future time horizon, commonly referred to as the system’s state of power (SoP). Battery system SoP is sensitive to multiple factors, such as battery state of health, state of charge, temperature, and their imbalances in multibattery systems. Analyzing such sensitivities is important for selecting appropriate system components and connection structure during the system design and for predicting substantial SoP changes to proactively guide the online power control. However, such sensitivity analyses are challenging since the SoP is not directly expressed in terms of these factors, and the SoP expression can become significantly complicated for interconnected heterogeneous battery cells. To address these challenges, qualitative and quantitative sensitivity analyses are first conducted for both series and parallel battery systems by deriving approximate expressions for the maximum system currents constrained by different operating limits. Some critical insights, commonly overlooked in industrial practices, have been revealed for improving the system SoPs. To pursue reliable analysis results, exact system SoPs are evaluated based on an accurate estimation method along with battery modeling parameters identified through experiments. Experimental tests are also performed to demonstrate some analysis results.